Blasting apparatus are commercially available for cleaning, degreasing, and deburring a wide variety of manufactured parts. Typical prior art blasting apparatus include a cabinet having a treating chamber into which a part mounted on a part support is conveyed for cleaning or deburring by a high pressure stream of water, steam, sand, grit, etc. discharged from sprayers located within the treating chamber. The construction of apparatus of this type includes a mechanism for moving the parts in and out of the treating chamber, a door or other structure for sealing the chamber once the parts are placed therein and spraying devices for discharging the cleaning material onto the parts in the treating chamber. Each of these features of prior art blasting apparatus, depending upon the particular design, have presented problems or limitations in operation.
Several different designs have been proposed to move parts in and out of the treating chambers of blasting apparatus. For example, in one type of apparatus a cabinet having a treating chamber is formed with an opening within which a door is mounted having a part support on its inner side. The door is placed in an open position to receive a part to be treated and then closed to place the part within the treating chamber for cleaning. Once the cleaning operation is completed the door is reopened to remove the treated part and replace it with another. See, for example, U.S. Pat. Nos. 4,213,475; 3,934,374; 4,143,669; 3,041,787; and, 4,741,351.
The problem with apparatus of this type is that the cleaning or blasting procedure is essentially a "batch" operation. That is, the apparatus must be shut down to both load a part onto the part support, and then, after the part is cleaned, to remove the clean part and replace it with another to be cleaned. This procedure is inefficient and involves a substantial amount of downtime of the machine as the parts are moved on and off the part support.
Another approach in the prior art for moving parts in and out of the treating chamber of a blasting apparatus involves the use of a turntable having a number of part supports along the circumference thereof which are movable in and out of the treating chamber by the rotation of the turntable. See, for example, U.S. Pat. Nos. 1,887,397 and 2,160,697. Alternatively, conveyors are employed which move parts continuously through a treating chamber. See U.S. Pat. No. 3,675,665. The use of a turntable or conveyor to move parts in and out of a treating chamber avoids some of the operating delays associated with the apparatus described above wherein a single part support is alternately moved in and out of a treating chamber. A number of parts can be supported on a turntable or a conveyor and the blasting apparatus is not shut down when the parts enter or leave the treating chamber.
One disadvantage of blasting apparatus having continuously movable turntables and/or conveyors is that it is difficult and possibly dangerous to load and unload parts while the part support is moving. Particularly where the parts to be treated are bulky and/or heavy, it is undesirable to attempt to remove a cleaned part from a support on rotating turntable or moving conveyor, and then replace it with a part to be treated before the turntable or conveyor moves the part support back into the treating chamber.
Another aspect of blasting apparatus is the creation of a seal at the entrance to the treating chamber to avoid the loss of water, steam or particulate blasting material into the environment during a blasting operation. This has been a particular problem in apparatus of the type described above wherein the parts are continuously movable in and out of the treating chamber because a dynamic seal must be created between the support for the parts and the entrance to the treating chamber.
In the prior art, flexible flaps or curtains have been used in an attempt to create a seal between a moving part support and the entrance to the treating chamber such as shown, for example, in U.S. Pat. Nos. 1,887,395 and 2,258,634. These types of seals are relatively ineffective in preventing the escape of material into the atmosphere and cannot create a fluid-tight seal of the treating chamber. Although a recovery system could be employed within the treating chamber, e.g., a vacuum/filter system to create a negative pressure therein and draw the cleaning material toward the base of the treating chamber, such a feature would add substantial expense to the blasting apparatus.
Another aspect of blasting apparatus is to ensure that the cleaning material sprayed onto the parts within the treating chamber completely covers the parts to remove all dirt, grease, burrs, etc. Prior art designs have included mechanisms for rotating or tilting the part support relative to spray devices, for moving the spray devices with respect to the part support and/or some combination of part support and sprayer movement. In many prior art apparatus, the mechanisms for moving the sprayers and/or the part supports are positioned within the treating chamber and are exposed to the water, steam, sand or grit employed to clean the part. See, for example, U.S. Pat. Nos. 2,160,697; 3,309,818; and, 4,299,245. The problem with this design is that the mechanisms can become worn and/or fouled with the cleaning material causing downtime of the blasting apparatus, and added expense for the repair or replacement of such mechanisms.